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JAMB Mathematics 1981 Question 1

Question 1

Variation

Suppose x varies inversely as y, y varies directly as the square of t and x = 1 when t = 3. Find x when t = 1/3

  1. A.81
  2. B.27
  3. C.1/9
  4. D.1/27
  5. E.1/81
Show the answer and explanation

Answer: A (81)

Explanation

x ∝ 1/y and y ∝ t², so x = k/t². x = 1 at t = 3 gives k = 9. At t = ⅓, x = 9 ÷ (1/9) = 81.